Fused circuit interrupter

ABSTRACT

A FUSED CIRCUIT INTERRUPTER COMPRISING A HOUSING WITH A MANUALLY OPERABLE INTERRUPTER STRUCTURE SUPPORTED ON THE HOUSING AND A REMOVABLE FUSE UNIT REMOVABLY SUPPORTED ON THE HOUSING IN ELECTRICAL SERIES WITH THE CONTACTS OF THE SWITCH STRUCTURE. THE CIRCUIT INTERRUPTER INCLUDES STRUCTURE FOR PREVENTING REMOVAL OF THE FUSE WHEN THE INTERRUPTER STRUCTURE IS IN THE &#34;ON&#34; OR CONTACT CLOSED POSITION. THE CIRCUIT INTERRUPTER ALSO INCLUDES STRUCTURE FOR PREVENTING THE OPERATION OF THE INTERRUPTER CONTACTS TO THE CLOSED POSITION WHEN THE INTERRUPTER CONTACTS ARE OPEN AND THE FUSE UNIT IS REMOVED. MEANS ARE ALSO PROVIDED TO PREVENT THE INSERTION OF A FUSE HAVING A RATING THAT IS HIGHER THAN IS DESIRABLE.

United States Patent inventors James P Ellsworth:

Glenn R. Thomas, Beaver, Pa.

Appl. No. 652,624

Filed July 11, 1967 Patented June 28, 1971 Assignee Westinghouse Electric Corporation Pittsburgh, Pa.

Continuation of application Ser. No. 518,133, Jan. 3, 1966, now abandoned.

FUSED CIRCUIT INTERRUPTER Primary Examiner-Bernard A. Gilheany Assistant Examiner- Dewitt M. Morgan AttorneysA. T. Stratton, Clement L. Mcl-lale and W. A.

Elchik ABSTRACT: A fused circuit interrupter comprising a housing with a manually operable interrupter structure supported on the housing and a removable fuse unit removab1y supported on the housing in electrical series with the contacts of the switch structure. The circuit interrupter includes structure for preventing removal of the fuse when the interrupter structure is in the on" or contact-closed position. The circuit interrupter also includes structure for preventing the operation of R f d the interrupter contacts to the closed position when the intere erences rupter contacts are open and the fuse unit is removed. Means UNITED STATES E S are also provided to prevent the insertion of a fuse having a 2,798,918 7/1957 Gelzheiser 337/84 rating that is higher than is desirable.

FIG. 2.

3 Sheets-Sheet 1 NONI! IIONOI Patented June 28, 1971 INVENTOR J es F. Ellsworth 0 Glenn R. Thomas BY MW 4 M ATTORNEY W|TNESSES= Patented June 28, 1971 3 Sheets-Sheet s 5 m 3 r Patented June 28, 1971 3 Sheets-Sheet 5 FIG. IO.

FIG. 9.

AMP

FIG. 13.

FIG. l2.

FIG. ll.

20 AMP l5 AMP ell.-

FUSE!) CIRCUIT INTERRUPTER This application is a continuation of our application entitled Fused Circuit Interrupter" Ser. No. l8,l33, filed Jan. 3. I966 and now abandoned.

This invention relates generally to fused circuit interrupters and more particularly to fused circuit interrupters of the type comprising a housing with a manually operable interrupter structure supported on the housing and a removal fuse unit removably supported on the housing in electrical series with the contacts of the switch structure.

A general object of this invention is to provide an improved fused circuit interrupter comprising a housing with a manually operable switch structure mounted in the housing and a fuse unit removably supported in the housing in electrical series with the contacts of the switch structure.

Another object of this invention is to provide an improved fused circuit interrupter comprising an insulating housing with a manually operable switch structure supported on the insulating housing and a fuse unit removably supported on the insulating housing, which fuse unit comprises an insulating fuse holder and a fuse removably supported on the insulating fuse holder for controlling the circuit through the contacts of the switch structure.

Another object of this invention is to provide an improved circuit interrupter comprising an insulating housing having opening means at the front thereof and an interrupter structure and fuse unit supported on the insulating housing, which interrupter structure is manually operable by means of a handle that protrudes through said opening means and which fuse unit comprises an insulating fuse holder removable through said opening means. Another object of this invention is to provide an improved fused circuit interrupter comprising an insulating housing and a manually operable interrupter structure supported on the insulating housing with a removable fuse unit removably supported on the insulating housing in electrical series with the contacts of the interrupter structure, which circuit interrupter comprises improved means for preventing removal of the fuse unit when the interrupter structure is in the on or contact-closed position.

Another object of this invention is to provide an improved circuit interrupter comprising a housing having an interrupter structure supported therein and a fuse unit removably mounted therein in electrical series with the contacts of the interrupter structure, which circuit interrupter comprises improved means for presenting operation of the interrupter contacts to the closed position when the interrupter contacts are open and the fuse unit is removed.

Another object of this invention is to provide an improved circuit interrupter comprising a housing having an interrupter structure supported therein and a fuse unit removably mounted therein in electrical series with the contacts of the interrupter structure, which circuit interrupter comprises improved means for preventing operation of the contacts to the closed position when the contacts are open and the fuse unit is not in the fully mounted position.

Another object of this invention is to provide an improvedcircuit interrupter comprising a housing having an interrupter structure supported therein and a fuse unit removably mounted therein in electrical series with the contacts of the interrupter structure, which circuit interrupter comprises improved means for preventing operation of the switch contacts to the closed position when the contacts are open and the fuse of the fuse unit is rated higher than is desirable for the particular rating of the circuit interrupter.

Another object of this invention is to provide an improved fused circuit interrupter comprising a housing having an interrupter structure supported therein and a fuse unit removably mounted therein, which circuit interrupter is constructed such that the interrupter structure will be operated to the off or contact-open position if a fuse unit is moved into the mounted position when the contacts are in the closed position.

Another object of this invention is to provide an improved fused circuit interrupter comprising an insulating housing having an interrupter structure mounted thereon and a removable fuse unit supported on the housing in electrical series with the contacts of the interrupter structure, which removable fuse unit comprises improved means for .providing a visual indication when the fuse blows.

Another object of this invention is to provide an improved fused circuit interrupter having increased utility and improved safety features.

These and other objects and advantages of the present in vention will become more apparent when considered in view of the following detailed description and drawings. In said drawings:

FIG. I is an end view, with parts broken away, of a circuit interrupter embodying principles of this invention;

FIG. 2 is a side view of the circuit interrupter of FIG. I, with the cover of the two-part insulating housing removed for the purpose of clarity;

FIG. 3 is a view similar. to FIG. l with the circuit interrupter shown in the "on" or contact-closed position;

FIG. 4 is a view similar to FIG. 2 with the removable fuse unit exploded to the removed position;

' FIG. 5 is a top plan view of the fuse unit of FIG. 4;

FIG. 6 is a view similar to the view of the fuse unit of FIG. 4, with parts broken away and with the fuse removed from the fuse unit;

FIG. 7 is a sectional view taken generally along the line VII-VII of FIG. 4;

FIG. 8 is a'view of the fuse unit of FIG. 4 taken along the lines VIII-VIII of FIG. 4, and with the fuse removed from the fuse unit;

FIG. 9 is a side view, with parts broken away, illustrating a position of the parts of the interrupter structure of FIG. 4 attained when an attempt is made to operate the switch structure to the closed position when the fuse unit is removed;

FIG. 10 is a side view, with parts broken away, of the circuit interrupter of FIGS. 1-8 having an overfused fuse unit mounted thereon, which view illustrates the position attained by the interrupter structure parts when an attempt is made to operate the interrupter structure to the closed position with an overfused fuse unit mounted on the housing of the circuit interrupter;

FIG. 11 is a side view, with parts broken away, illustrating the relative positions of a l5-amp fuse and IS-amp fuse terminal as they appear in the circuit interrupter of FIG. 2;

FIG. 12 is a view, similar to FIG. 11,- illustrating the relative mounted positions ofa 20-amp fuse andZO-amp fuse terminal FIG. 13 is a view, similar to FIGS. II and I2, illustrating the relative mounted positions of a SO-amp fuse and 30-amp fuse terminal.

Referring to the drawings, there is shown in FIGS. 1 and 2 a molded case-type circuit interrupter 3. The circuit interrupter 3 comprises a molded insulating housing comprising an opensided side part 5 of molded insulating material, which side part comprises a sidewall that is generally planar on the external side and that is formed to receive a circuit interrupter structure on the inner side, and which side part comprises wall means extending generally normal from the plane of the sidewall to form a cavity open at the side. The insulating housing also comprises a cover 7, also of molded insulating material, that covers the open side of the side part 5 to form an enclosed compartment inside of the insulating housing 5, 7. As can be seen in FIG. 2, there are four holes 9 in the side part 5 that align with four holes (not shown) in the cover 7 to receive four rivets that are used to fixedly secure the side part 5 and cover 7 together.

The circuit interrupter 3 comprises an interrupter structure 11 (FIG. 2) and a fuse unit 13, both of which are supported on the insulating housing 5, 7. If desired, the interrupter structure 11 could include a well-known type thermal and electromagnetic trip means automatically operable, in response to predetermined overloads, to operate the contacts to the open position.

The interrupter structure 11 comprises a stationary contact 15 and a movable contact 17 for cooperation with the stationary contact 15. The stationary contact is welded or otherwise suitably secured to a generally rigid line terminal conductor 19 that protrudes through an opening 21 in the bottom or back of the housing 5, 7. The terminal conductor 19 is bent over to provide a flat connecting part 23 that is disposed generally along a plane that is parallel to the plane of the bottom or back of the housing 5, 7. An opening 25 is provided in the connecting part 23 for receiving a connecting member that may connect the connecting part 23 to a bus bar whereby the terminal 19 can physically support the one end of the circuit interrupter 3 on a bus bar and electrically connect the contacts 15, 17 in series with the bus bar. The line terminal conductor 19 is moved into the open side of the housing part 5 during the assembling operation of the circuit breaker, and it is held in place by engagement with molded parts of the hoursing part 5. When the cover 7 is moved into position, the housing part 19 is secured in position on the housing 5, 7.

The movable contact 17 is welded or otherwise fixedly secured to one end of a rigid conducting contact arm 27. The contact arm 27 is generally U-shaped, and the opposite legs thereof engage in spaced pivot-support parts 29 formed on an insulating operating member 31. A metallic generally L shaped spring support 33 is supported on the housing part 5 with the short leg thereof being positioned in a notch 35 of the molded insulating housing part. A tension spring member 37 is supported at the lower end thereof in an opening in the bight portion of the generally U-shaped contact arm 27, and atthe upper end thereof in an opening in the free end of the metallic spring support 33. The spring 37 moves between the legs of the generally U-shaped contact arm 27. The molded insulating operating member 31 is provided with two pivot-pin parts 39 that are formed integral with the member 31 at opposite sides of the member 31, which pivot pin parts are supported in suitable bearing surfaces in the housing parts 5 and 7 to pivotally support the operating member 31 on the housing 5, 7. The operating member 31 is provided with a handle part 41 formed integral therewith, which handle part protrudes out through an opening 43 in the front of the housing part 5 to permit manual operation of the interrupter structure 11. A part 45 of the operating member 31 substantially closes the opening 43 in all positions of the handle 41. Oppositely disposed stop surfaces 47, formed integral with the operating .member 31, engages opposite internal stop surfaces 49,

formed integral with the housing part 5, to limit movement of the operating member 31 during operation of the interrupter structure 11.

A flexible conducting member 51 is connected at one end thereof to the contact arm 27 and at the other end thereof to a terminal conductor 53 (FIGS. 4 and 7) that is seated in a suitable depression in the insulating housing part 5. The terminal conductor 53 comprises a sheet metal generally U-shaped member having opposite legs 55 that extend outward from the plane of the paper as seen in FIG. 4. The legs 55 engage the housing cover 7 when the cover is moved into position to thereby provide support for the terminal 53 in the housing 5, 7. The terminal 53 is a sheet metal-type conducting member having some resilience, and the center part thereof is provided with a contact part 57 (FIGS. 4 and 7) that is stamped in the terminal for providing contact with another terminal in a manner that will be hereinafter specifically described. As can be seen in FIG. 7, the contact part 57 is formed at a part of the terminal 53 that is spaced at the other side from the housing 5 such that the member 53 can flex in a direction toward the housing to provide contact pressure when the fuse unit 13 is in the mounted position. As is best seen in FIGS. 4 and II, a load terminal conductor 61 is positioned in a suitable slot or opening 63 in the housing part 5, which slot or opening 63 leads out to an external part of the housing. A solderless terminal connector 65 is secured to the outer of the terminal conductor 61. The inner end of the terminal conductor 61 comprises a concave portion 67 for connection to a fuse terminal 69 of a fuse 71. The inner end of the terminal conductor 61 also comprises a stop portion 73 for limiting inward movement of the fuse 71 in a manner to be hereinafter specifically described. The fuse 71 may be a current limiting fuse with an interrupting rating of [000,000 amperes. During the assembly operation, the terminal conductor 61 and solderless connector 65 are moved into position through the open side of the housing part 5, with the terminal conductor 61 being positioned in the slot 63, and when the cover 7 is secured to the housing part 5, the terminal conductor and connector 65 are captured in place.

As was hereinbefore described, when the circuit interrupter 3 is assembled the terminal conductors 19 and 61 are dropped into position in the open side of the housing part 5 to be retained in place by molded formations of the housing part 5. The operating member 31, spring support 33, contact arm 27, operating spring 37, conductor 51, and terminal 57 are then moved into position as a unit in the open side of the housing part 5, and thereafter the cover 7 is placed over the open side of the housing part 5 to capture the parts in place. Four rivets are then passed through the four openings 9 (FIG. 2) in the housing part 5 and cover 7 to rivet the housing parts 5, 7 together.

The circuit interrupter 3 also comprises the fuse unit 13 that will be best understood with reference to FIGS. 2-6 and 8. The fuse unit 13 comprises an insulating fuse holder 75 having an upper generally U-shaped spring clip 77 supported thereon. The spring clip 77 comprises two leg parts 79 (FIGS. 4 and 8) and a bight portion 81. The bight portion 81 is disposed at the outside of a wall portion 83 (FIG. 8) of the insulating housing 75 and the legs 79 extend through suitable openings in the wall 83. The fuse clip 77 is secured to the wall 83 by means of a suitable rivet 85. The lower part of the insulating fuse holder 75 is generally L-shaped in cross section and this lower part comprises the wall 83 and another wall 87 extending generally normal to the wall 83. A fuse terminal connector 89, comprising a sheet metal resilient member of conducting material, is riveted to the lower part of the wall 83 by means of two rivets 91. The fuse connector 89 comprises a first generally planar part that receives the rivets 91 and two leg parts 93 that extend generally normal to the planar part that is secured to the wall 83. The fuse connector 89 also comprises a lower bent over part 95 that serves as a stop to limit the lengthwise dimension of any fuse that is to be mounted on the fuse holder. The part 95 insures that the fuse will be removed with the fuse holder. As can be understood with reference to FIGS. 2-6 and 8, the fuse 71 can be readily moved into connection with the fuse connectors 77, 89 with the upper spring-type fuse clip connector 77 retaining the fuse 71 in position. The fuse 71 is readily replaceable when the fuse unit 13 is removed from the insulating housing 5, 7. As can be seen in FIGS. 4-5 and 8, the insulating fuse holder 75 comprises a handle part 97 that is provided with an opening therein for receiving an indicating lamp 99. An opening 101 (FIG. 6) is provided at the front of the handle part 97 to provide an external visual indication from the front of the circuit interrupter when the lamp 99 is energized. A resistor 103 is connected in series with the lamp 99. The resistor and lamp 99 are connected to the fuse connectors 77 and 89 by means of an insulated upper conductor 105 that is connected, at an uninsulated part thereof, to the fuse spring clip connector 77 at the rivet 85 and an insulated lower conductor 107 that is connected, at an uninsulated part thereof, to the fuse holder 75 between the part 89 and the backwall 83 when the fuse connector 89 is riveted to the wall 83. It can be readily understood that the resistor 103 and lamp 99 are in parallel with the fuse 71 and in series with the interrupter contacts 15, 17 so that when the fuse 71 blows the lamp 99 will be energized to provide a visual indication that the fuse has blown.

As is best seen in FIG. 4, the housing part 5 is provided with an opening 109 at the front thereof to receive the fuse unit 13. When the fuse 71 is moved into the mounted position on the fuse holder 75 (FIG. 4), the upper fuse terminal 111 engages the spring clip connector 77 and the lower fuse terminal 69 engages the lower connector 89. The opposite legs 79 of the spring clip connector 79 are biased against the terminal 111 to hold the fuse 71 in position on the fuse holder 75. As can be understood with reference to FIGS. 2, 4, 7 and 8, the housing 5. 7, the members 61, 53 and the parts of the fuse unit 13 are constructed such that when the fuse unit 13 is moved from the position seen in FIGS. 4 and 8 to the position seen in FIG. 2, the lower terminal 69 of the fuse 71 will be biased against the parts 67, 73 of the load terminal conductor 61 by means of the leg part 93 of the spring-type connector 89 and the spring terminal 53 will be flexed to bias the contact part 57 thereof against the bight portion 81 (FIG. 8) of the upper fuse clip 77 to thereby automatically connect the fuse 71 in series with the contacts 15, 17in the circuit interrupter.

With the fuse unit 13 in position and the contacts 15. 17 are in the closed position, the circuit through the circuit interrupter 3 extends from the line terminal 19 through'the contacts 15, 17, the contact arm 27, the flexible conductor 51, the terminal 53 (FIGS. 4 and 7). the upper fuse connector 77. the upper fuse terminal 111, through the fuse, the lower fuse terminal 69, the lower connector 89, the load terminal conductor 61, to a conducting line that would be connected to the terminal conductor 61 by means of the solderless terminal connector 65. As was previously described, the resistor 103 and lamp 99 are in parallel with the fuse 71 and in series with the contacts 15, 17 so that the lamp 99 will be energized when the fuse blows in response to an overload above a predetermined value in the circuit of the circuit interrupter 3.

The interrupter structure 11 of the circuit interrupter 3 is shown in the open position in FIG. 2. In order to close the contacts 15, 17, the operating member 31 is moved by operation of the handle part 41 in a counterclockwise (FIG. 2) direction about the pivots 39 from the off" to the on" position. During this movement the contact arm 27, moving with the pivot parts 29 of the operating member 31 will be forced downward and to the right with the end 112 of the contact arm 27 initially sliding against a flat surface 113 of a rigid projection 115 that is molded integral with the housing part 5. After this initial movement a rigid metallic hook 117 is welded to the cohtact arm 27 will engage a flat surface 118 on a rigid projection 119 that is molded integral with the insulating fuse holder 75 to take over the function of restraining movement to the right of the contact arm 27. The hook 117 will slide off of the surface 118 and on to the surface 113. This movement continues until the line of action of the spring 37 through the spring supports is past the pivot 29 of the contact arm 27 whereupon the spring 37 will snap the contact arm 27 to the closed position seen in FIG. 3. When it is desired to operate the interrupter structure 11 to the "off position, the operating member 31 is moved about the pivots 39 from the on" position to the "off" position. During this movement the line of action of the spring 37 through the spring supports moves past the pivot 29 whereupon the spring 37 will operate to snap the contact arm 27 to the open position seen in FIG. 2. The contact arm 27 is stopped in the position seen in FIG. 2 when the part 112 thereof engages the surface 113 on the housing part 5.

The upper surface 125 (FIGS. 4 and 7) of the projecting part 115 of the insulating housing part 5 is positioned such that if an attempt is made to operate the interrupter structure 11 from the off" to the on" position when the fuse unit 13 is removed the part 112 on the contact arm will slide along the surface 113 and the hook 117 will move over the upper surface 125 on the rigid projection 115 to engage the surface 125 (FIG. 9) and prevent movement of the contact arm 27 and operating member31 to the "on" or contact-closed position. Thus, it can be understood that a worker will not be able to inadvertently operate the interrupter structure 11 to the on" position when the fuse unit 13 is removed. Thus, if the fuse unit 13 is out of place it can be understood that a person with a screwdriver or wire will not be able to accidentally or intentionally close a circuit through the terminals 53, 61.

The insulating housing part 5 is formed with spaced track surfaces 133 (FIG. 4) to receive opposite sides of the insulating fuse holder 75 to guide the fuse holder 75 into position during a mounting operation of the fuse unit 13.

If a worker moves a tool or other object into the opening 109 in the housing when the fuse unit is removed and pries the hook 117 off of the surface 125 to defeat the interlock and permit manual operation of the interrupter structure 11 to the "on position with the fuse unit removed. the switch structure 11 will be operated to the "off position when the fuse unit 13 is moved into the mounted position. As can be understood with reference to FIGS. 3 and 4, the part 47 of the insulating operating member 31, and the projection 119 on the insulating fuse holder 70 are positioned such that as the fuse unit 13 is guided downward between the tracks 133 the projection 119 of the fuse holder 75 will engage the part 47 of the operating member 31 to operate the operating member 31 far enough from the "on" to the "off" position to move the spring 37 overcenter whereupon the spring 37 will snap the contact arm 27 and operating member 31 to the open position before the fuse and fuse terminals are properly engaged. This prevents the possibility of having damaging prestriking arcs between the fuse connector 77 and the terminal 53 and between the terminal 69 and the terminal part 67 of the terminal conductor 61 during a mounting operation of the fuse unit 13. When the fuse unit is in the fully mounted position and when the interrupter structure 11 is in the "on" or closed position an operator cannot remove the fuse unit 13 from the housing 5, 7. Referring to FIG. 3, it will be noticed that when the fuse unit 13 is in the mounted position and when the interrupter structure 11 is closed the projection 119 on the insulating fuse holder 75 is disposed below a surface 139 on the rigid molded insulating operating member 31. If an attempt is made to remove the fuse unit 13 the projection 119 will engage the surface 139 tending to move the operating member 31 in a counterclockwise (FIG. 3) direction about the pivots 39. This counterclockwise movement of the operating member 31 is prevented because of the engagement of the stop surface 47 on the operating member 31 with a stop surface 49 on the insulating housing part 5. Thus, the fuse unit 13 cannot be removed when the switch structure 11 is in the closed position. This interlock, therefore, provides that damaging arcs will not be drawn between the fuse connector 77 and terminal 53 and between the terminal 69 and the terminal part 67 of the terminal conductor 61 during removal of the fuse unit 13.

As was previously described, during the closing operation of the interrupter structure 11 the part 112 ofthe contact arm 27 initially rides against the surface 113 of the projection 115 of the insulating housing part 5 for a very short distance and then the hook member 117, that is fixedly secured to the contact arm 27, rides first along the surface 118 of the projection 119 of the fuse holder housing 75 and then along the surface 113 of the projection 115 until the line of action of the spring 37 is overcenter relative to the contact arm 27 whereupon the contact arm 27 is snapped to the closed position by operation of the spring 37. If the fuse unit 13 is moved toward the fully mounted position and if for some reason the fuse unit 13 is not seated in the fully mounted position a space will appear between the projection 119 on the fuse holder 75 and the projection 115 on the housing part 5. Thus, during the attempt to close the interrupter structure 11 the hook part 117 on the contact arm 27 will move into this space to engage the stop surface on the projection 115 to thereby prevent operation of the interrupter structure 11 to the closed position. An operator then may release the handle 41 whereupon the spring 37 will move the contact arm 27 back to the fully open position. The operator can then move the fuse unit 13 down into the fully mounted position shown in FIG. 2 whereupon the interrupter structure 11 can be manually operated from the open to the closed position in the same manner hereinbefore described.

Improved means are provided for preventing overfusing of the fused circuit interrupter. Referring to FIGS. 11, 12 and'13, like parts are provided with like reference characters except that the parts of FIG. 12 are primed and the parts of FIG. 13 are double primed. As can be seen in these FIGS, the l5-amp fuse is the shortest in length; the 20-amp fuse is longer than the lS-amp fuse; and the 30-amp fuse is longer than the 20- amp fuse. The fuse holder 75 (FIGS. 3-6 and 8) will accept all three of the fuses disclosed in FIGS. "-13. As was previously described, the load terminal 61 is provided with a lower bent over stop part 73 (FIG. 11). When the fuse unit 13 is moved into the fully mounted position with a lS-amp fuse mounted thereon and with the IS-amp load terminal 6I mounted in the housing 5, 7, the fuse unit 13 can be mounted in the fully mounted position seen in FIGS. 2 and 3. and the interrupter structure 11 can be freely operated between the on" and "off" positions. If a ZO-amp fuse is mounted in the fuse holder 75, and if an attempt is made to mount the fuse unit 13 in the fully mounted position the lower fuse terminal 69' of the ZO-amp fuse 71 will engage the stop 73 of the IS- amp load terminal 61 and, since the fuse 71' cannot move upward (FIG. 10) in the fuse holder 75 past the position where it (the fuse 71) will engage a surface 126 on the insulating fuse holder 75, the fuse unit 13 will not reach the fully mounted position seen in FIGS. 2 and 3. Thus, there will be a space between the projection 115 on the housing part and the projection 119 on the fuse holder 75. Thus, if an attempt is made to operate the interrupter structure 11 to the on position with the longer, and therefore higher rated, fuse in the fuse holder 13 the hook part 117 on the contact arm 27 will fall into the space between the projections 115 and 119 to engage the stop part 125 on the projection 115 of the housing part 5 (FIG. to prevent a closing operation of the interrupter structure 11. The interrupter structure will be locked against a closing operation in the same manner if the longer 30-amp fuse is mounted in the fuse holder 75 and if the IS-amp terminal 61 is mounted in the housing 5,7.

As can be seen in FIG. 12, the load terminal 61 is provided with a stop 73 that is lower than the stop 73 of the load terminal 61 so that with a -amp fuse in the fuse unit 13 the fuse unit can be moved down to the fully mounted position seen in FIGS. 2 and 3. It will be understood, however, that if the longer -amp fuse is mounted in the fuse unit 13 and an attempt is made to mount the fuse unit 13 in the housing 5, 7 with only the 20-amp load terminal 69' in the housing the fuse unit 13 will not reach the fully mounted position and a space will be provided between the projections 119 and 115 (FIG. 10) of the fuse holder 75 and housing part5 respectively. The hook part 117 of the contact arm 27 will move into this space to engage the stop surface 125 of the projection 115 to thereby prevent a closing operation of the interrupter structure 11 in the same manner hereinbefore described. When the 30-amp load terminal 6l" (FIG. 13) is mounted in the housing 5, 7 a fuse unit 13 having the 30-amp fuse mounted thereon can be moved into the fully mounted position seen in FIGS. 2 and 3 to permit free operation of the interrupter-structure 11 in the same manner hereinbefore described.

Since numerous changes may be made in the abovedescribed apparatus and because different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim:

1. A fused circuit interrupter comprising an insulating housing opening means at the front thereof,

a circuit interrupter structure supported in said housing and comprising a stationary contact, a movable contact, a movable contact arm carrying said movable contact, a spring member, an insulating operating lever supported in said housing and comprising a handle part protruding out through said opening means at the front of said housing, said handle part being operable to move said insulating operating lever to operate said spring member and contact arm to open and close said contacts,

a fuse unit, comprising an insulating fuse holder and a fuse supported on said insulating fuse holder said fuse unit being movable into and out ofa fully mounted position on said housing through said opening means at the front of said housing, plug-in terminal means automatically connecting said fuse in electrical series with said contacts when said fuse unit is moved to the fully mounted portion,

a first latch means comprising a first stop means on said operating mechanism and a second stop means on said insulating housing, when said fuse unit is removed from said housing with said contacts in the open position and an attempt is made to operate said operating mechanism to close said contacts said first stop means engaging said second stop means to limit movement of said operating mechanism to thereby prevent closing of said contacts.

2. A circuit interrupter according to claim 1, and said first stop means on said operating mechanism comprising a stop member on said contact arm.

3. A fused circuit interrupter according to claim 1, and a second latch means operating automatically when said fuse unit is in the fully mounted position on said housing and said contacts are in the closed position to prevent removal of said fuse unit from said housing.

4. A fused circuit interrupter according to claim 3, and said second latch means comprising said insulating operating lever in the path of movement of said insulating fuse holder when said contacts are in the closed position.

5. A fused circuit interrupter comprising an insulating housing having opening means at the front thereof,

a circuit interrupter structure supported in said housing and comprising a stationary contact, a movable contact, an operating mechanism comprising a movable contact arm carrying said movable contact, spring means, an insulating operating member supported in said housing and comprising a handle part extending out through said opening means, said handle part being operable from an "off" position to an "on" position to move said operating member to operate said spring means and contact arm to close said contacts, said handle part being movable from said on" position to said off position to move said operating member to operate said spring means and contact arm to open said contacts,

a fuse unit removably mounted on said housing, said fuse unit comprising an insulating fuse holder and a fuse on said fuse holder, said fuse unit being movable into and out of a fully mounted position through said opening means, plug-in type terminal means automatically connecting said fuse in electrical series with said contacts when said fuse unit is moved to the fully mounted position,

a stop surface on said insulating housing and a stop part on said contact arm, said stop surface on said insulating housing being accessible when said fuse unit is removed such that if an attempt is made to operate said contacts to the closed position said stop part on said contact arm will engage said stop surface to prevent movement of said contact arm to the closed position, means on said fuse unit rendering said stop surface on said insulating housing inaccessible to said stop part on said contact arm when said fuse unit is in the fully mounted position whereby said contact arm can be freely operated between the open and closed positions when said fuse unit is in the fully mounted position.

6. A fused circuit interrupter comprising an insulating housing structure having opening means at the front thereof, a stationary contact supported in said insulating housing structure, a movable contact arm having a movable contact thereon and being supported in said insulating housing structure, spring means, an insulating operating member supported on said insulating housing structure and comprising an integral handle part extending out through said opening means, said insulating operating member being movable from an "off" position to an "on" position to operate said spring means and said contact arm to close said contacts, said insulating operating member being movable from said on" to said "off" position to operate said spring means and said contact arm to open said contacts, a first fuse connecting means supported in said insulating housing structure, a fuse unit comprising an insulating fuse holder and a fuse structure supported on said insulating fuse holder, said fuse structure comprising a fuse removably supported on said insulating fuse holder, said fuse structure comprising a second fuse connecting means, said fuse unit being movable through said opening means in said front of said insulating housing structure to a fully mounted position in which position said second fuse connecting means automatically engages said first fuse connecting means to connect said fuse in electrical series with said contacts, said l'use unit being a pullout unit removable through said opening means in said front of said insulating housing, and means on said fuse unit directly engaging said insulating operating member to prevent removal of said fuse unit when said insulating operating member is in said on" position.

7. A fused circuit interrupter comprising an insulating housing structure having opening means therein, a circuit interrupter structure supported in said housing structure, said circuit interrupter structure comprising a stationary contact and a movable contact, a contact arm supporting said movable contact, operating means comprising an operating member movable from an off position to an 011" position to move said contact arm to thereby move said movable contact into a closed position in engagement with said stationary contact, said operating member being movable from said on" position to said "of position to move said contact arm to thereby move said movable contact into an open position out of engagement with said stationary contact, a first fuse connecting means supported in said insulating housing structure, a fuse unit comprising an insulating fuse holder and a fuse structure supported on said insulating fuse holder, said fuse structure comprising a second fuse connecting means, said fuse structure comprising a first fuse having a length ofa first dimension and being removably supported on said insulating fuse holder, means on said insulating fuse holder for supporting a second fuse having a second length of greater dimension than said first length, said fuse unit being in a fully mounted position on said insulating housing structure with said second fuse connecting means in engagement with said first fuse connecting means to electrically connect said first fuse in electrical series with said contacts, said fuse unit being removable from said fully mounted position in the direction of the length of said fuse through said opening means when said contacts are open, said fuse unit being movable into said fully mounted position I in the direction of the length of said fuse through said opening means, stop means in said insulating housing structure for engaging a fuse longer than said first fuse to prevent movement of the fuse unit into the fully mounted position when a fuse longer than said first fuse is supported on said insulating fuse holder, and latch means for preventing operation of said contacts to the closed position when said fuse unit is prevented from being moved into the fully mounted position.

ll. A fused circuit interrupter comprising an insulating housing structure having a first opening means at the front thereof; a pair of cooperable contacts supported in said insulating housing structure; a movable contact arm carrying one of said contacts; operating means comprising an operating member extending from said first opening means and being movable between two operating positions to move said movable contact arm to thereby open and close said contacts; said insulating housing structure having a second opening means therein and a third opening means therein; a line terminal structure supported on said insulating housing structure and protruding through said second opening means; a load terminal conductor supported on said insulating housing structure at said third opening means and protruding through said third opening means; a fuse unit removably mounted on said insulating housing structure in electrical series with said line terminal structure, said contacts and said load terminal conductor; said load terminal conductor having stop means thereon; said fuse unit comprising an elongated fuse and being movable through said first opening means in the direction of elongation of said fuse' into a fully mounted position on said insulating housing structure; said stop means on said load terminal conductor being positioned to engage one end of said elongated fuse to limit the movement of said fuse unit toward the fully mounted position whereby a fuse unit with a longer fuse will be prevented from being moved into the fully mounted position; and latch means operating automatically when said fuse unit is prevented from being moved to the fully mounted position to prevent operation of said contacts to the closed position.

9. A fused circuit interrupter according to claim 8; said latch means comprising a latch part on said contact arm and a latch surface formed integral with said insulating housing to cooperate with said latch part to prevent movement of said contact arm to the closed position when the fuse unit is prevented from being moved to the fully mounted position. 

